Elevator car doors include one or more panels that are supported by an overhead rail and open and close by way of a door operator. It is common practice to drive one of the door panels from a point near the top of the panels. Other door panels, if center-opening or two speed arrangements are used, are driven by a cable relating device mounted above the guide rollers. The direct driven panel also carries a clutch that engages one of the hatch door panels. As in the case of the car door panels, the other hatch door panel or panels are cable-related at a point above the opening.
A sill is disposed below the door panels, and is formed with grooves. Plastic gibs, attached to the bottom of the door and hatch panels, project into the sill grooves for guiding the panels.
A typical center-opening door arrangement is illustrated in FIGS. 1 and 1a, labeled "prior art". The door panels 10, 11 hang on guide rollers 14 supported by an overhead rail 12. A door operator pulley and linkage "D" are coupled to one of the panels, e.g. 11, at a point "P" near the top of the panel, to move the panel between open and closed positions, in the direction of arrows 13. The driven panel 11 is connected to the non-driven panel 10 through a cable-relating device 34, 36 mounted above the door opening. The door panels 10 and 11 are attached to oppositely moving sections of cable 36a and 36b, at 17 and 15, respectively, to move in opposite directions. A clutch membrr 30 on the driven car door panel 10 engages a clutch member 32 on the corresponding hatch door panel, and the hatch panels are cable related by a mechanism similar to the cable 36 and pulleys 34 used for the car doors.
FIGS. 1 and 1a illustrate a conventional plastic guide gib 18, that is mounted by a bracket 16 to the bottom of the door 10 and projects into a groove 22 formed in the door sill 20. A similar groove arrangement is normally provided for the hatch doors.
The presence of guide grooves in the sill is a tripping hazard to passengers entering and leaving the elevator. The grooves create maintenance problems, since they can catch foreign objects and jam the doors. They also collect dirt (and water) from washing and, from an aesthetic standpoint, are somewhat unsightly.
Another weakness of known door systems is the inability to drive the panels at their center of percussion. During acceleration and deceleration of the doors, a moment is produced about the center of gravity "C", causing a pendulum effect, if the net force applied to the panels 10 and 11 is not along the center of percussion "CP", i.e. parallel to the direction of door movement 13 and through the center of gravity "C". As a practical matter, it is not possible to avoid such a pendulum effect in conventional door systems.
When the door operator D is actuated, the drive linkage D applies force to door panel 11 at point P. Clutch 30 and cable attachment 15 impart forces on the door panel 11 in the opposite direction. In practice, it is not possible to position all of these force-transmission points along the center of percussion CP. Driving the door panel along the center of percussion makes the pendulum effect of the cable-relating device worse. Positioning the clutch mechanism 30, 32 along the center of percussion of the hatch panel makes the pendulum effect on the car door worse. In the case of the driven panel 10, the drive force is imparted overhead, at 17. It is therefore also not possible to drive the driven panel, in a cable related drive, along its center of percussion.
Up-thrust rollers are usually installed to counteract this tendency. But, up-thrust rollers do not completely eliminate the problem because, for quietness, there must be running clearance between the up-thrust rollers and the track.